The present invention relates to a torque transducer, preferably intended to be used when measuring the torque in the outgoing crankshaft of automobile engines.
In the automobile industry there is a need of a torque transducer which shall be capable of being placed between the engine housing and the flywheel and which more or less surrounds the crankshaft. Since the space in the longitudinal direction is very limited here, there is no room for an annular torque transducer, for example of the type which is shown and described in U.S. Pat. No. 3,011,340. In addition, the power requirement and the cost of such a multi-polar transducer are far too high. A cruciform transducer according to U.S. Pat. No. 2,912,642 would be more favourable considering the power requirement and the cost, but using a normal, concentrated mode of construction such a transducer will surround only a small part of the circumference of the shaft and the shaft must therefore rotate practically a full turn before the internal stress configuration prevailing in the shaft surface has been scanned over the whole circumference, so that a measurement value independent of the internal stresses can be formed. Since the automobile industry desires a response time of at the most 50 ms, the lowest engine speed for correct measurement -- if the necessary filter time constant could be made negligible by using a high supply frequency -- would be 60 .multidot. 1000/50 = 1200 revolutions per minute, which is not acceptable. It must be possible to determine the torque at considerably lower engine speeds.